1. Field of the Invention
The present invention relates to a boat maneuvering control method for a boat and a boat maneuvering control system for a boat.
2. Description of the Related Art
A boat maneuvering control system for a boat is known in general. Such a boat maneuvering control system for a boat is disclosed in U.S. Pat. No. 7,214,110 and U.S. Pat. No. 7,361,067.
U.S. Pat. No. 7,214,110 discloses a boat maneuvering control system for a boat including an engine, a throttle mechanism that manipulates the output of the engine, and a microprocessor that controls the acceleration of the boat. The microprocessor of the boat maneuvering control system for a boat prepares an acceleration profile as a function of time by setting a target rotational speed, an acceleration rate, an overshoot rate, and an overshoot period and controls the rotational speed of the engine based on the prepared acceleration profile.
U.S. Pat. No. 7,361,067 discloses a boat maneuvering control system for a boat including an engine, a throttle device that manipulates the output of the engine, and a microprocessor that controls the acceleration of the boat. The microprocessor of the boat maneuvering control system for a boat learns and stores an actual acceleration profile of the boat and controls the rotational speed of the engine based on the stored acceleration profile.
In the control system for a boat described in each of U.S. Pat. No. 7,214,110 and U.S. Pat. No. 7,361,067, the engine (the rotational speed of the engine) is controlled based on the acceleration profile. When the engine is controlled by feedback control in a state where a target boat speed is set, however, it may take time for an actual boat speed to approach the target boat speed due to a delay in determining the actual boat speed of the boat with respect to a change in engine rotational speed or the like. In this case, responsiveness is disadvantageously poor. When a control gain is set high in order to improve responsiveness, an overshoot and hunting occur, and hence convergence is disadvantageously poor. Consequently, when the engine is controlled in the state where the target boat speed is set, it is difficult to achieve both responsiveness and convergence.